How do I Calculate Spell Damage?

[Fero]

I am mapping out some Blaster wizard builds. However, I am not sure how some meta-magic/meta-spell effects interact for the damage calculations. Does anyone know if WotC printed explicit rules or the community has reached a consensus on any of the following?

1→ How do multiple instances of +50% damage stack? For example, if you use Mark of the Enlightened Soul on a 20 CL Fireball augmented by Enervate Spell targeting an evil living target, what is the damage? Is it 10d6*(1+0.5+0.5), 10d6*(1.5*1.5) or something else? I am leaning toward the first option as it is consistent with how damage multipliers work for crits/uber-chargers, but am not sure.

2→ How do abilities that add damage per dice interact with damage multipliers? For example, if a CL 15 wizard with Cold Spell Specialization casts an Enervate Spell Cone of Cold, is the damage (15d6+30)*1.5 ot is it 15d6*1.5+30?

3→ Same question, but for abilities that add damage not calculated per dice? For example, Flash Frost adds +2 dmg per spell level. Would that get multiplied?

4→ Same question but for abilities that improve damage but are not inherently changing the spell (ray weapon specialization for example).

5→ Same question, but for abilities that add dice of damage, for example, the Ring of Mystic Fire or Black Lore of Moil? For example, does a CL 20 Enervated Moilian Vampiric Touch do 13d6*1.5 or 10d6*1.5+3d6?

6- On that note, how do extra dice interact with extra damage per dice? For example, if I use all of the charges from a Ring of Mystic Fire on a Fiery Fireball, does it do 14d6+10 or 14d6+14?

7→ Finally, would empower interact differently, as it increases all variable effects, not just damage?

[Beni-Kujaku]

The easy one, with explicit rules :

1) All instances of +50% in 3.5 stack as +50%*number of effects. If you have three effects that multiply your damage by 1.5, the final damage is 2.5 times the unmodified damage. Same thing with "double". It's in fact "+100%". So a spell that is both doubled and multiplied by 1.5 is in fact multiplied by 2.5. This is true for everything, except "real life values", such as weight or height.

The rest is covered by "you can apply beneficial effects in the most beneficial order". Therefore, you first add the dice of damage, then you add the fixed and "per dice" damage, then you multiply the total. This is consistent with the Combat Statistics rules quote below.

Do note that the "most beneficial order" is a quite nebulous term from the 3.5 FAQ and that you'll not find (that I know) a clearer RAW rule that takes every case into account. The same question takes as an example a creature with both resistance and weakness to an element, and says that it will first apply its resistance then its weakness. But what is beneficial to the creature is detrimental to the originator of the elemental attack. So my guess is that "the creature" in "most beneficial to the creature" is the one that uses or possesses the ability that modifies the damage.

In that case, we'd have first the user of the effect (U) then the target (T) using their effects, and the type of effect being adding dice (D), adding damage (A), substracting damage (S), multiplying damage (M) or dividing damage (R).
The order of application is then as follows:
UD>UA>UM>US>UR>TR>TS>TM>TA

[sleepyphoenixx]

I am mapping out some Blaster wizard builds. However, I am not sure how some meta-magic/meta-spell effects interact for the damage calculations. Does anyone know if WotC printed explicit rules or the community has reached a consensus on any of the following?

1→ How do multiple instances of +50% damage stack? For example, if you use Mark of the Enlightened Soul on a 20 CL Fireball augmented by Enervate Spell targeting an evil living target, what is the damage? Is it 10d6*(1+0.5+0.5), 10d6*(1.5*1.5) or something else? I am leaning toward the first option as it is consistent with how damage multipliers work for crits/uber-chargers, but am not sure.

Yes, it's the first option. All damage multipliers work that way.

Multiplying Damage

Sometimes you multiply damage by some factor, such as on a critical hit. Roll the damage (with all modifiers) multiple times and total the results. Note: When you multiply damage more than once, each multiplier works off the original, unmultiplied damage.


2→ How do abilities that add damage per dice interact with damage multipliers? For example, if a CL 15 wizard with Cold Spell Specialization casts an Enervate Spell Cone of Cold, is the damage (15d6+30)*1.5 ot is it 15d6*1.5+30?
See the first bolded part in the above quote. You multiply the entire damage after all modifiers, so it's (15d6+30)*1.5.


3→ Same question, but for abilities that add damage not calculated per dice? For example, Flash Frost adds +2 dmg per spell level. Would that get multiplied?
See above. It's a modifier so it gets multiplied.


4→ Same question but for abilities that improve damage but are not inherently changing the spell (ray weapon specialization for example).
See above.


5→ Same question, but for abilities that add dice of damage, for example, the Ring of Mystic Fire or Black Lore of Moil? For example, does a CL 20 Enervated Moilian Vampiric Touch do 13d6*1.5 or 10d6*1.5+3d6?
I'm pretty sure the exception to multiplying extra damage dice only applies to weapons, so i'd say the first. Not 100% sure on that one though.


6- On that note, how do extra dice interact with extra damage per dice? For example, if I use all of the charges from a Ring of Mystic Fire on a Fiery Fireball, does it do 14d6+10 or 14d6+14?
The ring adds xd6 of damage to your spell, Fiery Spell adds +1 damage per die. It depends on the specific wording for other effects but your example would definitely work imo.


7→ Finally, would empower interact differently, as it increases all variable effects, not just damage?
See again the rules quote. With all modifiers means with all modifiers so the extra dice get multiplied too.

[Darg]

I'm pretty sure the exception to multiplying extra damage dice only applies to weapons, so i'd say the first. Not 100% sure on that one though.

This is right. (https://www.d20srd.org/srd/equipment/weapons.htm#critical) The only questionable application of this is certain effects which don't add bonus damage such as a warlock's hideous blow or an enlightened fist delivering a touch spell as they are two separate sources of damage. Since it isn't explained anywhere, most people default to only multiplying weapon damage because "extra" damage dice aren't multiplied (https://www.d20srd.org/srd/combat/combatStatistics.htm#multiplyingDamage).

[Fero]

I'm pretty sure the exception to multiplying extra damage dice only applies to weapons, so i'd say the first. Not 100% sure on that one though.



Thank you for the fantastic answer. Regarding the language quoted above, would this mean that non-weaponlike spells multiply the extra dice but weaponlike spells do not? For example, of I used a Ring of Mystic Fire on an empowered Fireball, the damage would be 14d6*1.5 but if I turned that same empowered Fireball into a ray (Spellwarp Sniper, etc), it would instead do 10d6*1.5+4d6?

[Darg]

Thank you for the fantastic answer. Regarding the language quoted above, would this mean that non-weaponlike spells multiply the extra dice but weaponlike spells do not? For example, of I used a Ring of Mystic Fire on an empowered Fireball, the damage would be 14d6*1.5 but if I turned that same empowered Fireball into a ray (Spellwarp Sniper, etc), it would instead do 10d6*1.5+4d6?

Weaponlike spells are not weapons. They don't follow all the rules for weapons. The term "weaponlike" just means that they have an attack roll and function like a weapon in some ways. An example of this are that you are treated as armed while holding a touch spell and can make as many attacks as you are able until you discharge it. Another is that you don't add your strength bonus to damage when attacking with produce flame even though it doesn't mention you don't like flame blade does.

Turning a fireball into a ray doesn't change the damage calculation. It only modifies the area, no longer allows a save, and can crit.

If you need a quote:


All such spells deal damage as spells, not weapons